Reland of Add content type information to encoded images and corresponding rtp extension header

webrtc/common_types.h

Index: webrtc/common_types.h
diff --git a/webrtc/common_types.h b/webrtc/common_types.h
index e1a4c77d37adf184bb43b0fd87070d635f54d917..750420196d957bde26f094368c9a3cee11519196 100644
--- a/webrtc/common_types.h
+++ b/webrtc/common_types.h
@@ -18,6 +18,7 @@
 #include <string>
 #include <vector>
 
+#include "webrtc/api/video/video_content_type.h"
 #include "webrtc/api/video/video_rotation.h"
 #include "webrtc/base/checks.h"
 #include "webrtc/base/optional.h"
@@ -716,6 +717,11 @@ struct RTPHeaderExtension {
   bool hasVideoRotation;
   VideoRotation videoRotation;
 
+  // TODO(ilnik): Refactor this and one above to be rtc::Optional() and remove
+  // a corresponding bool flag.
+  bool hasVideoContentType;
+  VideoContentType videoContentType;
+
   PlayoutDelay playout_delay = {-1, -1};
 };